Automatic test equipment such as, for example, that used for testing avionics systems, requires internally generated stimuli corresponding to particular parameters to be tested. A common parameter to be tested by test equipment of the type described is synchro/resolver shaft angle, i.e. the angular position of a synchro/resolver shaft. Prior to the present invention apparatus for generating synchro/resolver shaft angle stimuli has been somewhat cumbersome, requiring complicated circuitry including switching arrangements and the like. This has been particularly true when stimuli corresponding to various shaft angles need to be generated.
Commonly assigned U.S. Pat. No. 4,703,307 issued on Oct. 27, 1987 to the present inventors contemplates apparatus of the type described including a plurality of channels each having a digital to synchro/resolver converter for converting digital signals to AC analog synchro/resolver signals, and at least one channel having a synchro/resolver to digital converter for converting the analog signals to digital signals for measurement purposes. The digital to synchro/resolver converters are responsive to digital signals containing different shaft angle information, and to an AC reference signal which provides a carrier for the analog signals. Each of the digital to synchro/resolver converters is independently controlled and simultaneously operated to provide output analog signals with different shaft angle information; different carrier signal phase angles; and different output amplitudes. Computer interface logic generates control signals for controlling the apparatus in accordance with the above.
The present invention, on the other hand, relates to apparatus comprising analog and digital components for generating synchro/resolver stimulus signals in any arbitrary shaft angle sequence automatically and under control of an external computer interface logic. The disclosed configuration features solid state implementation, thus eliminating electrical/mechanical components. The configuration achieves relatively high resolution and repeatability as is desirable for the purposes described. Moreover, the invention features a self-test capability for "wrap-around" testing of the stimulus signals to insure the integrity of the apparatus, as required for the aforenoted applications.
Accordingly, it is the object of the present invention to provide apparatus for generating synchro/resolver stimulus signals with high resolution and repeatability characteristics and including self-test capability.